Decision Feedback Equalizer
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Abstract
A decision-feedback equalizer (DFE) samples an analog input signal against M references during the same symbol time to produce M speculative samples. Select logic in the DFE then decodes N bits resolved previously for previous symbol times to select one of the M speculative samples as the present resolved bit. The present resolved bit is then stored as the most recent previously resolved bit in preparation for the next symbol time. The select logic can be can be programmable to accommodate process, environmental, and systematic variations.
2 Citations
20 Claims
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1. (canceled)
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2. An equalizer comprising:
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M samplers to sample an analog signal during a given symbol time, each of the M samplers to sample the analog signal with respect to a corresponding one of a range of sample instants and a corresponding one of a range of reference levels to produce M speculative samples; select logic to convey a selected one of the M speculative samples as a presently resolved bit; and storage to store N previously resolved bits, where 2̂
N is less than M;the select logic to select the presently resolved bit based on a correspondence between the N previously resolved bits and the M speculative samples. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of equalizing an analog signal, the method comprising:
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sampling the analog signal during previous symbol times to obtain N previously resolved bits; storing the N previously resolved bits in storage; sampling the analog signal during a present symbol time with respect to M references and M phases to obtain M speculative samples; selecting one of the M speculative samples as a presently resolved bit using select logic defining a correspondence between the N previously resolved bits and the M speculative samples; storing the presently resolved bit in the storage as a most-recent previously resolved bit; and varying ones of the M phases relative to one another to select preferred sample instants. - View Dependent Claims (13, 14, 15, 16)
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17. An equalizer comprising:
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an analog-to-digital converter (ADC) to sample an analog signal with respect to M references and M phases during a symbol time to produce M speculative samples; means for decoding N previously resolved samples of the analog signal to select one of the M speculative samples, wherein M is not 2̂
N, and wherein the means for decoding provides a programmable correspondence between the N previously resolved samples and the M speculative samples; andmeans for updating the previously resolved samples to include the selected one of the M speculative samples. - View Dependent Claims (18, 19, 20)
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Specification